1. Field of the Invention
This invention relates to a system and method for scanning a supervised region to detect and extinguish a fire occurring anywhere on the floor or wall of said region.
2. Description of the Related Art
Applicant's European patent application No. EPA-0098235 discloses an automatic fire extinguishing system in which when a fire detector for general monitoring detects the occurrence of a fire, a pair of fire source detecting apparatuses are driven to determine the position of the source of such fire and a nozzle which sprays fire extinguishing fluid is directed to that position, such position being computed by a central processing unit from the detection data provided by the fire source detecting apparatuses.
In the foregoing system, a pair of fire source detecting apparatuses each include a detector for detecting a fire source, and vertical and horizontal control means for driving the detector in the vertical and horizontal directions. When the general monitoring fire detector detects a fire, the horizontal and vertical control means drive the respective fire source detecting apparatuses so that the respective detectors comprised therein scan in the horizontal and vertical directions for the direction of the fire source.
More particularly, the vertical deflection angle of each of the detectors is initially set substantially downward. When a fire source is not detected during the first scanning operations, the vertical control means of the respective fire source detecting apparatuses is driven to reset the deflection angle of the corresponding detector by a predetermined angle upward from the original downward setting. After completion of resetting of the vertical deflection angle, the corresponding horizontal control means is driven to cause the corresponding detector to scan in the horizontal direction for the fire source. Similar searching operations are repeated until the fire source is detected. The deflection angles are set so that the successive directions of the detector are at equal angular intervals.
In such an automatic fire extinguishing system, the minimum size flame which is to be regarded as a fire is assumed to be a reference fire source, and such reference fire source is to be detected in the course of the horizontal scanning. However, since the deflection angles of the detector in the vertical direction are set at the same predetermined equal angular intervals over the entire supervised region extending from near to the fire source detecting apparatus to a position remote therefrom, there is the following problem. If the vertical deflection angles are determined based on a reference fire source located at a remote position in the supervised region, the change in the deflection angles for fire sources nearer to the detector become narrow and scanning distance on the floor of the supervised region also becomes narrow. As a result, the required number of scanning cycles is increased and rapid fire source detection cannot be attained. On the other hand, if the vertical deflection angles are determined based on a reference fire source located near to the fire source detecting apparatus, the change in the vertical deflection angles for fire sources further from the detector becomes large and results in proportionately large changes in distance to such sources. Therefore, it is necessary to subdivide the preset unit deflection angles in order to accurately detect fire sources in intermediate positions.